Jet propulsion boat

Abstract

To provide a jet propulsion boat which can be efficiently propelled by disposing a steering nozzle closer to the bottom of the boat. A jet propulsion boat includes a jet propulsion apparatus driven by an engine at the stern. A jet nozzle for jetting water is provided at the rear portion of the jet propulsion apparatus. A steering nozzle is swingably supported by the jet nozzle so as to adjust the direction of a stream of water jetted from the jet nozzle. In the jet propulsion boat, an outlet side of the jet nozzle is covered with an inlet side of the steering nozzle and the vertical diameter D 2 of the inlet of the steering nozzle is set to be smaller than the transverse diameter D 1 of the inlet.

What is claimed is:  
     
       1. A jet propulsion boat comprising: 
       a jet propulsion apparatus driven by an engine at the stern;  
       a jet nozzle for jetting water provided to the rear portion of the jet propulsion apparatus;  
       a steering nozzle swingably supported on the jet nozzle for adjusting the direction of a stream of water jetted from the jet nozzle;  
       an outlet of said jet nozzle is covered with an inlet of said steering nozzle; and  
       a vertical diameter of the inlet of said steering nozzle is set to be smaller relative to a transverse diameter of the inlet of the steering nozzle;  
       wherein said steering nozzle includes a maximum wide that is offset upwardly relative to a centerline passing through the transverse diameter of said steering nozzle for assuring an enlarged steering angle.  
     
     
       2. The jet propulsion boat according to  claim 1 , wherein the steering nozzle is mounted to be inclined upwardly and to the rear with respect to an axis of the jet nozzle. 
     
     
       3. The jet propulsion boat according to  claim 2 , wherein mounting supports are provided for securing the steering nozzle relative to the jet nozzle with a predetermined angle of inclination being formed therebetween. 
     
     
       4. The jet propulsion boat according to  claim 1 , wherein said steering nozzle has a circular truncated cone shape wherein the diameter is gradually reduced towards the rear of the jet propulsion boat with flat portions being formed on upper and lower portions on the inlet side. 
     
     
       5. The jet propulsion boat according to  claim 4 , wherein said flat portion formed on the upper portion of the inlet side of the steering nozzle extends a predetermined distance and the flat portion formed on the lower portion of the inlet side of the steering nozzle extends a predetermined distance for forming the vertical diameter of the inlet of the steering nozzle to be smaller relative to the transverse diameter of the inlet of the steering nozzle. 
     
     
       6. The jet propulsion boat according to  claim 5 , wherein said jet propulsion boat includes a bottom and said flat portion formed on the lower portion of the inlet side of the steering nozzle enables said steering nozzle to be disposed in close proximity to the bottom of said jet propulsion boat. 
     
     
       7. The jet propulsion boat according to  claim 1 , wherein on lateral sides of the jet nozzle a first spacing is provided between an outer surface of said jet nozzle and an inner surface of said steering nozzle that is enlarged relative to a second spacing formed on the vertical diameter between an outer surface of said jet nozzle and an inner surface of said steering nozzle for assuring an enlarged steering angle. 
     
     
       8. A steering nozzle for use on a jet propulsion boat comprising: 
       a jet nozzle for jetting water therefrom;  
       a steering nozzle swingably supported on the jet nozzle for adjusting the direction of a stream of water jetted from the jet nozzle;  
       an outlet of said jet nozzle is covered with an inlet of said steering nozzle; and  
       a vertical diameter of the inlet of said steering nozzle is set to be smaller relative to a transverse diameter of the inlet of the steering nozzle;  
       wherein said steering nozzle includes a maximum wide that is offset upwardly relative to a centerline passing through the transverse diameter of said steering nozzle for assuring an enlarged steering angle.  
     
     
       9. The steering nozzle for use on a jet propulsion boat according to  claim 8 , wherein the steering nozzle is mounted to be inclined upwardly and to the rear with respect to an axis of the jet nozzle. 
     
     
       10. The steering nozzle for use on a jet propulsion boat according to  claim 9 , wherein mounting supports are provided for securing the steering nozzle relative to the jet nozzle with a predetermined angle of inclination being formed therebetween. 
     
     
       11. The steering nozzle for use on a jet propulsion boat according to  claim 8 , wherein said steering nozzle has a circular truncated cone shape wherein the diameter is gradually reduced towards the rear of the jet propulsion boat with flat portions being formed on upper and lower portions on the inlet side. 
     
     
       12. The steering nozzle for use on a jet propulsion boat according to  claim 11 , wherein said flat portion formed on the upper portion of the inlet side of the steering nozzle extends a predetermined distance and the flat portion formed on the lower portion of the inlet side of the steering nozzle extends a predetermined distance for forming the vertical diameter of the inlet of the steering nozzle to be smaller relative to the transverse diameter of the inlet of the steering nozzle. 
     
     
       13. The steering nozzle for use on a jet propulsion boat according to  claim 12 , wherein said jet propulsion boat includes a bottom and said flat portion formed on the lower portion of the inlet side of the steering nozzle enables said steering nozzle to be disposed in close proximity to the bottom of a jet propulsion boat. 
     
     
       14. The steering nozzle for use on a jet propulsion boat according to  claim 8 , wherein on lateral sides of the jet nozzle a first spacing is provided between an outer surface of said jet nozzle and an inner surface of said steering nozzle that is enlarged relative to a second spacing formed on the vertical diameter between an outer surface of said jet nozzle and an inner surface of said steering nozzle for assuring an enlarged steering angle.